Sr3AlO4F晶体中掺杂Ba2+,Ca2+离子占据不同Sr2+格位倾向性的第一性原理研究

通过比较第一性原理计算总能量得出碱金属离子Ba2+和Ca2+取代占据氟氧化物晶体Sr3AlO4F中两种不同Sr格位时,Ba2+倾向占据10配位的Sr(1)位,而Ca2+倾向占据8配位的Sr(2)位,与实验分析结果一致.基于上述优化结构,通过键价求和计算和畸变指数分析,得出Sr3AlO4F中Sr(1)格位离子严重未饱和成键,倾向于被较大Ba2+离子取代占据;而Sr(2)格位离子略微过饱和成键,倾向于被较小Ca2+离子取代占据.     

KPb2Cl5晶体中掺杂Er3+和Eu3+离子占据格位倾向性的原子模拟研究

本文采用经验势原子方法模拟研究了稀土Er3+和Eu3+离子掺入KPb2Cl5晶体的格位占据情况,其中经验势参数通过拟合KPb2Cl5、PbCl2、ErCl3、EuCl3晶体结构得到.在此基础上,研究了KPb2Cl5晶体的本征缺陷和替代缺陷,而且通过溶解反应能计算发现,掺杂Er3+/Eu3+离子更倾向于占据Pb2格位,并由最近邻的K空位缺陷提供电荷补偿.这一结论与文献报道的KPb2Cl5:Eu3+光谱分析结果一致,为Er3+掺杂KPb2Cl5占据格位实验假设提供理论支持.     

一类奇异半正三阶三点边值问题解的存在性

笔者研究了一类三阶三点边值问题解的存在性,在非线性项半正且奇异的情况下,利用Guo—Kmsnoselskii不动点定理证明了解的存在性．     

Terahertz-field-induced insulator-to-metal transition in vanadium dioxide metamaterial

Electron-electron interactions can render an otherwise conducting material insulating, with the insulator-metal phase transition in correlated-electron materials being the canonical macroscopic manifestation of the competition between charge-carrier itinerancy and localization. The transition can arise from underlying microscopic interactions among the charge, lattice, orbital and spin degrees of freedom, the complexity of which leads to multiple phase-transition pathways. For example, in many transition metal oxides, the insulator-metal transition has been achieved with external stimuli, including temperature, light, electric field, mechanical strain or magnetic field. Vanadium dioxide is particularly intriguing because both the lattice and on-site Coulomb repulsion contribute to the insulator-to-metal transition at 340?K (ref. 8). Thus, although the precise microscopic origin of the phase transition remains elusive, vanadium dioxide serves as a testbed for correlated-electron phase-transition dynamics. Here we report the observation of an insulator-metal transition in vanadium dioxide induced by a terahertz electric field. This is achieved using metamaterial-enhanced picosecond, high-field terahertz pulses to reduce the Coulomb-induced potential barrier for carrier transport. A nonlinear metamaterial response is observed through the phase transition, demonstrating that high-field terahertz pulses provide alternative pathways to induce collective electronic and structural rearrangements. The metamaterial resonators play a dual role, providing sub-wavelength field enhancement that locally drives the nonlinear response, and global sensitivity to the local changes, thereby enabling macroscopic observation of the dynamics. This methodology provides a powerful platform to investigate low-energy dynamics in condensed matter and, further, demonstrates that integration of metamaterials with complex matter is a viable pathway to realize functional nonlinear electromagnetic composites.     

Studies on biomechanics of skeletal muscle based on the working mechanism of myosin motors: An overview

Skeletal muscle is the source of human body motion.Many scholars have been studying in this field to reveal its contraction mechanism,and relevant achievements have been awarded the Nobel Prize.This paper reviewed the current researches on biomechanics of skeletal muscle,and concluded two strategies(top-down and bottom-up methods) for the biomechanical research of skeletal muscle.Moreover,this paper generalized two major aspects of muscle research:(1) the multi-force coupling mechanism and the collective operation mechanism of molecular motors;(2) the bioelectrochemical driving and control principium of muscle contraction.We discussed the solution for experimental verification and induced a novel idea to study the biomechanics of skeletal muscle based on the microscopic working mechanism of molecular motor,which is the origin of muscle contraction.Finally we analyzed the disadvantages in existent researches and explored future directions that need further studies.     

Efficient synthesis of functionalized 2-pyridones by ytterbium chloride catalyzed tandem condensation

An efficient method was developed for the synthesis of arylidene heterobicyclic 3-cyano-2-pyridones via ytterbium chloride catalyzed tandem condensation of aromatic aldehydes,cyclic ketones,and cyanoacetamide.The conditions and scope of the reaction were investigated and a reaction mechanism was proposed.     

钢管混凝土拱—钢腹板PC箱型系梁组合桥梁

为减轻钢管混凝土拱梁组合体系桥的自重,提出了采用钢腹板(平钢腹板或波纹钢腹板)代替PC箱形系梁的混凝土腹板,从而形成钢腹板PC箱形系梁。以一座已建成的钢管混凝土拱梁组合体系桥为原桥,进行了钢腹板PC箱形系梁的试设计研究。结果表明,试设计桥由于减小了自重下的内力,降低了面内自振频率,从而改善了原桥的静力和抗震性能。此外,试设计桥经济性好且方便施工,说明钢管混凝土拱—钢腹板PC箱型系梁组合桥梁是可行的。     

正形置换的Walsh谱特征

在研究多输出Boole函数Walsh循环谱的基础上,利用多输出Boole函数的正交性与其坐标函数任意组合函数的平衡性之间的等价关系,证明了一个置换f(x)是正形置换的充要条件是其Walsh循环谱W(f)(α,α)=W(f)(0,α)=0.     

异色瓢虫雌虫多次交配的利益

本文研究了多次交配对异色瓢虫雌虫的产卵量、孵化率和雌虫寿命的影响。结果表明:多次交配显著提高了异色瓢虫雌虫的产卵量和孵化率,缩短了异色瓢虫雌虫的寿命;单次交配和重复交配对异色瓢虫的产卵量、孵化率和雌虫寿命没有显著影响。可能是不同雄虫间的精子竞争提高了精子质量,导致异色瓢虫雌虫进行多次交配产卵量和孵化率提高。多次交配中,不同雄虫间激烈的交配竞争和交配干扰给雌虫身体造成的物理损伤可能是雌虫寿命缩短的原因。     

Microstru cture and oxygen storage capacity of Sr-modified Pt/CeO2 –ZrO2catalysts

Strontium was introduced into CeO2–ZrO2 mixed oxides (CZ) by doping and impreg-nation metho ds, and then Pt was impregnated on the Sr-modifie d CZ to obtain the catalysts. X-ray diffraction (XRD), X-photon spectra (XPS), high-resolution transmission electronic microscopy (HRTEM) and H2 temperature programmed reduction (TPR) were carried out to characterize the micro-structure and reducibility of catalysts. The oxygen storage capacity (OSC) was evaluated with CO serving as probe gas. The results showed that the incorporation of Sr₂₊ in the lattice of CZ could promote the OSC properties by increasing the structure defects and enhancing the diffusion rate of oxygen from bulk to surface. For the Sr-impregnated sample, the strong metal–support interaction (SMSI) between Pt and CZ was interrupted, since Sr covered parti al surface Ce species. Such interruption retarded the back-spillover effect occurring at the Pt/Ce interface at low temperature, resulting in the loss of OSC. Meanwhile, it was found that a part of impregnated Sr₂₊ could partially diffuse from the surface to the inner atomic layers of CZ and partially incorporated in the lattice during the calcination. The OSC performance of Sr-impregnated sample therefore climbed remarkably with the rise of temperature.